Display device

ABSTRACT

A display device is provided, in which a member for sealing a liquid crystal is formed at sides of a pair of opposing substrates, so that a space other than an effective display region is made small and a substrate size is reduced. The pair of substrates is bonded to each other with a predetermined gap provided therebetween by an adhesive layer, and a liquid crystal injected in the gap is sealed in. The adhesive layer is formed closely to the sides of the substrates, so that a space where a sealing material is conventionally formed becomes unnecessary and the substrate size is made small. Moreover, a tape close to the adhesive layer is fixed to the sides of the substrates, so that an outer peripheral portion of the substrates is protected against impact, contamination, and electrostatic breakdown, and handling is simplified.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a flat panel type display device, suchas a liquid crystal display device or an organic EL display device,which is used for an information equipment, such as a computer or aportable terminal, or for an Audio Visual equipment such as a largescreen television.

2. Description of the Related Art

FIGS. 7A and 7B simply show the structure of a conventional liquidcrystal display device. FIG. 7A is a front view and FIG. 7B is asectional view taken along the line A-A′ of FIG. 7A.

The liquid crystal display device includes a pair of substrates whichare a TFT substrate 1 having a pixel matrix circuit and a drivercircuit, and an opposite substrate 2 on which a color filter is formed.The substrates 1 and 2 are opposite to and bonded to each other, and aliquid crystal material 5 is sealed in a gap between the substrates by asealing material. Reference numeral 3 denotes an external connectionterminal for connecting a driver circuit formed on the TFT substrate 1to an external power source circuit or the like.

The liquid crystal 5 is sealed in by a sealing material 4 formed on aperipheral portion of the substrate 1 or 2. The sealing material 4 isformed on the surface of the substrate 1 or 2 by a dispenser system, ascreen printing method, or the like. A liquid crystal injection port isformed in a part of the sealing material 4, and is sealed with anadhesive 6 after the liquid crystal 5 is injected.

Since the sealing material 4 is formed on the surface of the substrate 1or 2, the size of the substrate becomes large by the width of thesealing material 4 itself or a margin in a sealing material providingstep. For example, a nozzle diameter of a dispenser is about 100 to 300μm, and a sealing material with this width is linearly drawn on thesurface of a substrate resulting that the width of the sealing material4 becomes about 1 mm when the substrates 1 and 2 are bonded to eachother.

As shown in FIGS. 7A and 7B in the conventional device, the sealingmaterial for sealing the liquid crystal material is formed on thesurface of the substrate, so that the area of the substrate becomeslarger than an effective display portion, which prevents miniaturizationof the display device.

At present, a manufacturing technique of a polysilicon TFT has beenestablished, and a liquid crystal display device in which a drivercircuit and a pixel matrix circuit are integrated, is in plentifulsupply. However, a substrate area becomes larger than an effectivedisplay region by the formation of the driver circuit. It is desirablethat a space other than a display region is as small as possible in viewof miniaturization of a device or getting multiple pieces. Thus, amethod of disposing a sealing material on a driver circuit has beenemployed.

However, since glass filler for regulating a cell gap (an intervalbetween substrates) is generally mixed in the sealing material, when thesealing material is disposed on the driver circuit, the filler givesdamage and stress to the driver circuit. Moreover, since the drivercircuit has a surface roughness larger than a pixel matrix circuit, itis very difficult to uniformly keep the cell gap on the driver circuitby the filler.

Moreover, an active type display device has a problem of heat generationsince an insulating substrate, such as a glass substrate or quartzsubstrate, is used as a substrate. The thermal conductance coefficientof the sealing material is relatively small so that heat radiation isinsufficient, and there is also a problem of detachment due to heatexpansion and contraction.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a display device inwhich the above described problems due to a sealing material is solvedand a substrate size of a flat panel type display device is reduced.

In order to solve the above problems, the structure of a display deviceof the present invention is characterized in that the display devicecomprises a pair of substrates which are opposite to and are bonded toeach other with a predetermined gap provided therebetween, an adhesivelayer formed closely to the sides of the pair of substrates, and a tapeor a frame member formed closely to the adhesive layer.

That is, in the display device of the present invention, a sealingmaterial is not formed on the surface of the substrate, but the memberfor bonding the pair of substrates to each other and for sealing the gaptherebetween is formed at the sides of the substrates.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1D are explanatory views of a sealing member of embodiment1;

FIG. 2 is an explanatory view showing the shape of sides of substratesof the embodiment 1;

FIGS. 3A to 3C are plan views and a sectional view showing an oppositesubstrate and a TFT substrate of the embodiment 1;

FIGS. 4A to 4D are explanatory views of a sealing member of embodiment2;

FIGS. 5A to 5C are explanatory views of the structure of a gap holdingmember of embodiment 3;

FIGS. 6A to 6E are sectional views for explaining manufacturing steps ofthe gap holding member of the embodiment 3; and

FIGS. 7A and 7B are a front view and a sectional view of a conventionalliquid crystal display device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The best mode for carrying out the present invention will be describedwith reference to FIGS. 1A to 1D. In this embodiment, the presentinvention is applied to a liquid crystal display device. A pair ofsubstrates 101 and 201 are bonded to each other, with a predeterminedgap provided therebetween, by an adhesive layer 302 formed at the sidesof the substrates, and a liquid crystal 310 injected in the gap issealed in. FIGS. 1B and 1C are sectional views of portions “a” and “b”of FIG. 1A.

By forming the adhesive layer 302 at the sides of the substrates 101 and201, a space where a sealing material is conventionally formed becomesunnecessary, so that the substrate size can be made small.

Moreover, by forming a tape 301 closely to the adhesive layer 302 at thesides of the substrates, the outer peripheral portions of the substratescan be protected against impact, so that handling becomes easy.Moreover, since the tape 301 separates the adhesive layer 302 from anouter environment, it is possible to obtain an effect of preventingcontamination and deterioration of the adhesive layer 302, so that thereliability of the display device is improved.

For the purpose of bonding and fixing the tape 301 to the sides (endsurfaces) of the substrates 101 and 201 through the adhesive layer 302,as shown in FIG. 1D, an adhesive 300 is first disposed on the tapelinearly. Then, as shown in FIGS. 1B and 1C, the tape 301 is wound onthe sides of the pair of substrates 101 and 201 and the adhesive 300 ishardened.

In the following, the preferred embodiments of the present inventionwill be described in detail with reference to FIGS. 1 to 6.

Embodiment 1

This embodiment shows an example in which the present invention isapplied to an active type liquid crystal display device in which adriver circuit is integrated. FIG. 3A is a front view of a TFTsubstrate, FIG. 3B is a front view of an opposite substrate, and FIG. 3Cis a schematic sectional view of the TFT substrate and the oppositesubstrate.

The TFT substrate is manufactured by using a well-known manufacturingtechnique of a polysilicon TFT. As shown in FIG. 3A, on a substrate 101,there are provided a pixel matrix circuit 102 including a pixelelectrode formed for each pixel and a TFT (active element) connected tothe pixel electrode, a gate driver circuit 103 and a source drivercircuit 104 for driving the TFT of the pixel matrix circuit 102, and anexternal connection terminal 105. An FPC is connected to the externalconnection terminal 105. It is appropriate that a glass substrate,quartz substrate, or the like, which is transparent to visible light, isused as the substrate 101. In the case where a reflection type liquidcrystal display device is manufactured, the substrate 101 at the TFTsubstrate side is not limited to a transparent substrate, but a siliconsubstrate or the like may be used.

Besides, the structure of the TFT substrate is not limited to that shownin FIG. 3A. For example, it is possible to enumerate a redundantstructure in which two driver circuits are provided at both sides of apixel matrix circuit, and a structure in which other circuits, such as apre-charge circuit, are integrated in addition to a driver circuit. Thestructure of the TFT substrate does not limit the structure of thepresent invention.

A plurality of TFT substrates are formed on one substrate, and aftercompletion, the substrate is divided into a predetermined shape. Asshown in FIG. 3C, in this embodiment, shaping is made so that the side(end surface) of the divided substrate 101 becomes taper-shaped.Incidentally, although the end surface on the side where the externalconnection terminal 105 is formed is flat, the end surface on the sidewhere the external connection terminal 105 is formed may also be shapedinto a taper.

On the other hand, for the manufacture of the opposite substrate, asubstrate of glass, quartz, or the like, which is transparent to visiblelight, is prepared. When the substrate is for color display, a colorfilter is formed on a region 202 opposite to the pixel matrix circuit102 on the substrate. An opposite electrode 206 made of a transparentconductive film of ITO or the like is formed to cover at least theregion 202 of the substrate 201. Next, similar to the TFT substrate, thesubstrate is divided into a predetermined shape. Four sides (endsurfaces) of the divided substrate 201 are tapered.

In the dividing step of the substrates 101 and 201, if a dicer is used,dividing and working of a side (end surface) can be carried out in thesame step. Alternatively, it is also possible to polish the end surfaceafter dividing is carried out by breaking subsequently to scribing. InFIG. 3B, reference numerals 203 and 204 denote regions opposite to thegate driver circuit 103 and the source driver circuit 104, respectively.

After the completion of the dividing step, a not-shown orientation filmfor orienting a liquid crystal is formed on the outermost surface of theTFT substrate and the opposite substrate, and a rubbing process iscarried out.

Next, spherical spacers for holding a cell gap are dispersed on one ofthe TFT substrate and the opposite substrate. Then, as shown in FIG. 3C,the TFT substrate and the opposite substrate are made opposite to eachother, and the pair of substrates 101 and 201 are bonded to each otherwhile maintaining the gap regulated by the spacers. In this embodiment,a sealing member for bonding the substrates and for sealing a liquidcrystal is formed at the sides of the substrates 101 and 201. A tapeprovided with an adhesive is used as this sealing member. Amanufacturing method of the sealing member for a liquid crystal will bedescribed below with reference to FIGS. 1A to 1D.

As shown in FIG. 1D, an adhesive 300 made of UV setting resin islinearly disposed on a long tape 301 by a dispenser. Then, as shown inFIG. 1A, the tape 301 with the adhesive 300 inside is wound around thesides of the substrates 101 and 201 so as to close the gap between thebonded substrates 101 and 201. At this time, a liquid crystal injectionport is left.

The substrate 201 has such a shape that in the state where the substrate201 is bonded to the TFT substrate, the substrate 201 covers thecircuits 102 to 104 of the TFT substrate and does not cover the externalconnection terminal 105, so that the circuits 102 to 104 on the TFTsubstrate are protected by the substrate 201. The surface of thesubstrate 101 where the external connection terminal 105 is formed,protrudes from the side of the substrate 201, so that connection to anFPC can be easily made.

For the purpose of miniaturizing a liquid crystal display device, it ispreferable that the side (end surface) of the substrate 101 does notprotrude from the side (end surface) of the substrate 201. Besides, itis designed to prevent such a state that the substrate 101 protrudes sothat the pixel matrix circuit 102 and the driver circuit are exposed.Here, the side of the substrate 201 is made almost coincident with theside of the substrate 101.

FIGS. 1B and 1C are sectional views schematically showing portions “a”and “b” in FIG. 1A, respectively. That is, the portion “a” shows aportion where the TFT substrate protrudes from the opposite substrate,and the portion “b” shows a portion where the sides (end surfaces) ofthe substrate 101 and the opposite substrate 201 are almost coincidentwith each other.

As the tape 301 used for the sealing member, it is possible to use ametallic material having high heat conductivity, such as an aluminum orcopper tape, or a material having humidity resistance, such as a papertape coated with resin or aluminum. For the adhesive 300, in addition tothe UV setting resin, it is possible to use a thermosetting resinmaterial that is set at a relatively low temperature such as roomtemperature.

The linearly disposed adhesive 300 has suitable viscosity, and as shownin FIGS. 1B and 1C, when the tape 301 is wound around the sides (endsurfaces) of the substrates 101 and 201, the adhesive 300 is pressed andspread almost all over the surface of the tape 301, so that the adhesionof the tape 301 is ensured. Then the tape is irradiated with UV light sothat the adhesive 300 is hardened. The gap between the substrates 101and 201 and the sides of portions where the two substrates are oppositeto each other are covered with the sealing member made of the tape 301through the adhesive layer 302, and the substrates 101 and 201 arebonded to each other with a predetermined gap provided therebetween.

Moreover, in this embodiment, for the purpose of enhancing the sealingeffect and protecting the edge of the substrate, the tape 301 is, like aframe, made to cover not only the sides of the substrates 101 and 201but also the peripheries of the surfaces of the substrates 101 and 201which are exposed in the state where the substrates are bonded to eachother. At the portion “a” where the substrate 101 protrudes from thesubstrate 201, the tape is formed so as to cover the protruding surfaceof the substrate 101 and the outer surface of the substrate 201. At theportion “b” where the substrates 101 and 201 are opposite to each other,the outer surfaces of the substrates 101 and 201 are also covered by thetape. However, it is important that the portion of the tape covering theouter surfaces of the substrates 101 and 201 does not overlap with aneffective display region. Besides, it is preferable to fix the tape sothat the driver circuits 103 and 104 are covered, and when thisstructure is adopted, it is possible to prevent a photo leak currentfrom flowing in the driver circuits.

After the adhesive layer 302 is hardened, a liquid crystal 310 isinjected from the liquid crystal injection port. Then the liquid crystalinjection port is also covered by the tape 301 provided with theadhesive 300 as shown in FIG. 1D. At this time, the end of thepreviously wound tape is made to overlap with the end of the tape forclosing the injection port. Through the above steps, as shown in FIGS.1A and 1B, the structure where the liquid crystal 310 is sealed in thegap between the substrates 101 and 201 by the sealing member isobtained. Incidentally, in FIGS. 1A and 1B, circuits and oppositeelectrodes formed on the substrates 101 and 201 are omitted.

In this embodiment, it is unnecessary to dispose a sealing material onthe surface of a substrate, so that a substrate size can be reduced, andcontrary to the conventional sealing material, damage or stress is notapplied to a driver circuit. Moreover, as shown in FIG. 3A, it ispossible to reduce margins M1 to M4 from the edge of the substrate 101(201) to the circuits 102 to 104 (regions 202 to 205 opposite to thecircuits).

In this embodiment, as shown in FIGS. 1B and 1C, the end faces of thesubstrates 101 and 102 are tapered, so that the end faces of the bondedsubstrates 101 and 201 together form a wedge-shaped space, and theadhesive 300 collects in this space. Thus, it becomes difficult for theadhesive 300 to intrude into the space between the substrates 101 and201. Moreover, since a contact area between the adhesive 300 and thesubstrates 101 and 201 is increased, the adhesion strength can beraised.

Since the adhesive layer 302 is designed not to intrude into the spacebetween the substrates 101 and 201, as the foregoing margins M1 to M4,it is sufficient if only margins in the dividing step are taken intoconsideration. In the case where a scriber dicer is used in the dividingstep, the values of the margins M1 to M4 can be lowered down to about0.5 mm, and in the case where a dicer is used, the values can be lowereddown to the range of 0.5 mm to 0.1 mm.

For the purpose of making the margins M1 to M4 small, it is better as aportion of the adhesive 300 intruding into the space between thesubstrates 101 and 201 gets smaller. Thus, the adhesive 300 with arather low viscosity is not preferable, and it is important to make theadhesive have a suitable viscosity.

As methods of decreasing the intrusion of the adhesive 300, it ispossible to enumerate a method in which as shown in FIG. 1D, the tape301 is wound while the adhesive 300 is disposed thereon by a dispenser,and at the same time, the adhesive 300 is sequentially hardened byirradiation of UV light toward the wound portion, and a method in whichthe adhesive 300 disposed on the tape 301 is irradiated with UV light sothat the adhesive is hardened a little.

Moreover, in order to obtain the above effects, other than the structurein which the end surfaces of the substrates 101 and 201 are tapered, theend surfaces may be shaped like a step as shown in FIG. 2. Besides, inthis embodiment, although the substrate 101 at the TFT substrate side isalso tapered, when only the end surfaces of the opposite substrate 201is shaped like a taper or a step, similar effects can be obtained.Incidentally, if the viscosity of the adhesive 300 is so high that theadhesive does not intrude into the space between the substrates, it isalso admissible that the end surfaces of the substrates remain flat asin the conventional substrate.

Conventionally, since the sealing material is provided on the surface ofthe substrate, the outer peripheral portion of the substrate is in sucha state that the portion beetles, like a hood, from the sealingmaterial, so that the outer peripheral portion of the substrate is verybrittle against a mechanical impact. Thus, in order to protect thesubstrate against the impact, in addition to an encasement in a finalproduct form, the pair of substrates with the sealed liquid crystal ismounted in an outer frame (made of aluminum or plastics) and is made amodule.

On the other hand, in this embodiment, the outer peripheral portions(including the gap, end surfaces, and outer surfaces) of the substrates101 and 201 are protected by the sealing member. Thus, the conventionalouter frame for a module becomes unnecessary, so that the display devicecan be made miniaturized and lightweight.

In the sealing member of this embodiment, since the gap between thesubstrates is covered with the adhesive layer 302, the liquid crystal issubstantially sealed with the adhesive layer 302, and simultaneously,the substrates 101 and 201 are bonded to each other. However, in caseonly the adhesive layer made of a resin material is used, protectionagainst impact or contamination is not sufficient. Then, by bonding andfixing the tape 301 to the gap between the substrates 101 and 201 andthe sides (end surfaces) thereof through the adhesive layer 302, thestrength of the outer peripheral portion of the substrate can beincreased, and it is possible to prevent impurities from intruding intothe liquid crystal material. Thus, handling of the substrate becomeseasy, and it also becomes possible to handle the substrate by hand.

Further, by bonding and fixing the tape 301, an effect of preventingelectrostatic breakdown of the TFT substrate can be obtained. Ingeneral, for the purpose of preventing the electrostatic breakdown inmanufacture of a TFT, a wiring line for an internal short is formed sothat the potential of the TFT substrate is made uniform. Then, in orderto prevent the electrostatic breakdown in a product state, after thestep of liquid crystal injection, the end of the wiring line for aninternal short is polished obliquely so as not to be in contact with anend protruding outside of the conventional sealing material. However,the end of the wiring line is not completely protected.

On the contrary, in this embodiment, the side (end surface) of thesubstrate 101 is covered with the tape 301, so that contact with awiring line for an internal short is prevented, and also in view ofelectrostatic breakdown, handling becomes easy and operation efficiencyis improved.

In the case where the tape 301 is not provided but the adhesive isapplied and hardened to form only the adhesive layer 302, if bubbles aremixed in the adhesive, the adhesive is hardened while the bubblesremain, so that the reliability of the adhesive layer 302 is lowered. Onthe contrary, when the tape 301 is also fixed to the side (end surface)of the substrate, the adhesive 300 before hardening can be pressedthrough the tape 301 when the tape 301 is wound on the side (endsurface) of the substrate, so that the bubbles in the adhesive 300 canbe driven out.

Moreover, in the driver integration type liquid crystal display deviceas in this embodiment, there is a problem of heat generation in thedriver circuit. However, in the liquid crystal display TFT, theinsulating substrate of glass, quartz, or the like is used, and the heatconductivity of the sealing material is also low, so that it isdifficult to effectively diffuse heat. Thus, a tape of a metal materialsuch as aluminum, which has heat conductivity higher than the insulatingsubstrate and the adhesive layer 302, or a tape coated with such a metalmaterial is used as the tape 301, so that a heat diffusing function canbe provided.

Especially in this embodiment, since the distance (substrate margins M1to M4) from the tape 301 to the circuits 103 and 104 is small, heat fromthe circuits 103 and 104 can be effectively diffused to the tape 301.Moreover, since the tape 301 is in close contact with the adhesive layer302, the tape has an effect of preventing the detachment of the adhesivelayer 302 due to heat expansion and contraction.

Incidentally, in FIG. 1A, although the tape 301 is not bonded to the endof the substrate 101 where the substrate protrudes from the oppositesubstrate 201, if the tape 301 is also fixed to the end of this portionand the edge of both surfaces through the adhesive layer 302, theprotection of the edge of the substrate 101 becomes more certain.

Embodiment 2

This embodiment is a modified example of the embodiment 1, and a framemember is used instead of the tape 302. This embodiment will bedescribed with reference to FIGS. 4A to 4D. Incidentally, in FIGS. 4A to4D, the same reference numerals as those of FIGS. 1 to 3 denote the samemembers.

First, as described in the embodiment 1, after spacers are dispersed, asubstrate 101 constituting a TFT substrate is made opposite to asubstrate 201 constituting an opposite substrate. Then, an adhesive madeof thermosetting resin is disposed inside of frame members 401 and 402divided into two pieces as shown in FIG. 4A. A liquid crystal injectionport 402 a is provided in the frame member 402, and care must be takennot to clog the injection port 402 a with the adhesive. FIGS. 4C and 4Dare sectional views showing portions “a” and “b” of FIG. 4A,respectively. The end surfaces of the substrates 101 and 201 are taperedsimilarly to the embodiment 1.

It is appropriate that the frame members 401 and 402 are formed of amaterial similar to a conventional outer frame for making a module. Forexample, the frame members can be formed of a metallic material, such asaluminum, aluminum alloy, stainless, or copper, or a resin material suchas plastic.

As shown in FIG. 4B, the frame member 401 and 402 are attached to theouter peripheral portions of the substrates 101 and 201, and theadhesive is hardened by heating. As shown in FIGS. 4C and 4D, the framemembers 401 and 402 are fixed to the substrates 101 and 201 through theadhesive layer 403. Here, although the adhesive is applied to the sidesof the frame members 401 and 402, the adhesive may be applied to the endsurfaces of the substrates 101 and 201.

After a liquid crystal 410 is injected through the liquid crystalinjection port 402 a, a cap, which is fitted in the injection port 402 aand is made of the same material as the frame members 401 and 402, isbonded and fixed to the injection port 402 a by an adhesive. The liquidcrystal 410 is sealed in the gap between the substrates 101 and 201 bythe sealing member composed of the adhesive layer 403 and the framemembers 401 and 402.

As shown in FIG. 4D, the section of the frame members 401 and 402 isC-shaped, and the members cover the peripheries of the outer surfaces ofthe substrates 101 and 201. On the other hand, like the portion “a” ofthe frame member 401, the sectional structure of the portion where thesubstrate 101 protrudes from the substrate 201 is such that as shown inFIG. 4C, the frame member covers the surface of the protruding substrate101.

By this shape, the two frame members 401 and 402 can continuously coverthe outer peripheries (end surfaces, gap, and outside surfaces) of thesubstrates 101 and 201 through the adhesive layer 403. The frame members401 and 402 are set so as not to overlap with the pixel matrix circuit102 which becomes an effective display region. Here, as shown in FIG.4B, the frame members 401 and 402 are designed so as to cover the drivercircuits 103 and 104. A window is bored in the frame member 401 so thatthe external connection terminal 105 is connected to an FPC.

The sealing member of this embodiment is composed of the frame members401 and 402 fixed to the substrates 101 and 201 through the adhesive403, and similar effects to the sealing member using the tape in theembodiment 1 can be obtained. It becomes possible to set the margins M1to M4 (see FIG. 3A) of the substrate within the range of 0.1 to 0.5 mmas described in the embodiment 1. Particularly, since the frame membersare used, protecting effects against mechanical impact, contamination,and static electricity are higher than those of the tape, and theadhesive layer 403 with little bubbles can be formed with reliability.Moreover, as set forth in the embodiment 1, when the frame member ismade of a metallic material, such as aluminum, having heat conductivityhigher than the adhesive layer 403, heat generated in the driver circuitcan be effectively diffused.

The airtightness of the frame members 401 and 402 is sufficient if theliquid crystal does not leak, it is not necessary to form the adhesivelayer 403 on the whole surface of the inside of the frame members 401and 402, but the adhesive layer may be partially provided to a degreethat the frame members can be fixed to the substrates 101 and 201.

In this embodiment, although the frame member constituting the sealingmember is divided into two pieces, it may be divided into four piecesfor every side, or even in the case where it is divided into two pieces,it may be divided into upper and lower portions. In the case where theliquid crystal display device is a reflection type, it is also possibleto adopt such a structure that the frame members cover all the outsidesurface of the TFT substrate 101.

Embodiment 3

This embodiment shows an example in which the sealing members of theembodiments 1 and 2 are combined. First, as described in the embodiment1, a tape is fixed to the outer peripheral portions of substratesthrough an adhesive, and then, as described in the embodiment 2, framemembers are bonded and fixed by the adhesive.

In the case where the liquid crystal display device of the embodiments 2or 3 is used as a light bulb of a reflection type display device, theframe members 401 and 402 of the sealing member can be used as framesfor encasement.

In this case, the sealing member is formed as shown in FIG. 3A, and anFPC is connected to the external connection terminal 105. Then themember covering the exposed surface (except a display region) of thesubstrate 101 is fixed by an adhesive or the like, so that a light bulbis completed.

Although the description of the embodiments of the present invention hasbeen made on a liquid crystal display device, if the present inventionis applied to a display device, such as an organic EL display, having astructure in which a pair of substrates are bonded to each other, it ispossible to easily make the display device miniaturized and lightweight.Moreover, handling is simplified, and operation efficiency is improved.Moreover, in the case where the present invention is applied to a drivercircuit integration type active matrix display device, it is possible toeffectively diffuse heat generation in a circuit on a substrate.

Embodiment 4

A conventional sealing material is disposed on the surface of asubstrate, and filler is mixed in the sealing member, so that it ispossible to regulate a cell gap. On the other hand, the sealing memberof the embodiments 1 to 3 is disposed at the sides (end surfaces) of thesubstrates, so that it does not regulate a cell gap. Although sphericalspacers are dispersed in addition to filler in order to regulate thecell gap, there is also a case that a substrate on which the sphericalspacers are dispersed can not be kept in a sufficient horizontal stateuntil the sealing member of the embodiment is bonded and fixed to thesubstrate.

In order to solve such problems, in this embodiment, holding means of acell gap suitable for a liquid crystal display device using the sealingmember shown in the embodiments 1 to 3 will be shown. This embodimentwill be described with reference to FIGS. 5A to 5C and FIGS. 6A to 6E.

FIGS. 5A to 5C are structural views of a gap holding member 511 of thisembodiment, FIG. 5A is a top view of the gap holding member 511, andFIG. 5B is a perspective view. FIG. 5C is a view schematically showing asectional structure of a liquid crystal display device in accordancewith this embodiment.

The gap holding member 511 is a cylindrical member made of polyimidewhich is one of photosensitive resin materials, and is formed on anopposite side substrate 501. Reference numerals 502, 503, and 504 denoteregions corresponding to a matrix circuit, a gate driver circuit, and asource driver circuit of a TFT substrate, respectively. Referencenumeral 510 denotes an opposite electrode formed on the region 502.

Forming steps of the gap holding member 511 will be described below withreference to FIGS. 6A to 6E. First, a glass substrate or quartzsubstrate constituting the opposite substrate and having transparency isprepared. In this embodiment, the glass substrate 501 is used. Atransparent conductive film is formed on the glass substrate 501 and ispatterned so that the opposite electrode 510 is formed on the region 502opposite to the matrix circuit 102 (FIG. 6A). In this embodiment, an ITOfilm with a thickness of 150 nm was formed as the transparent conductivefilm. If necessary, a color filter or a black matrix is formed beforethe opposite electrode 510 is formed.

Next, as shown in FIG. 6B, a photosensitive polyimide film 51 with athickness of 3.2 μm was formed by a spin coating method. Thereafter, forthe purpose of flattening the surface of the photosensitive polyimidefilm 51 over the entire surface of the opposite substrate, the film wasallowed to stand still for 30 minutes at room temperature (leveling).Next, the photosensitive polyimide film 51 was pre-baked for 3 minutesat 120° C.

Since a cell gap (an interval between substrates) is determined by thethickness of the photosensitive polyimide film 51, the thickness of thephotosensitive polyimide film 51 is suitably determined according to thecell gap. For example, it is appropriate that the thickness isdetermined so that the cell gap becomes about 4 to 6 μm for atransmission type liquid crystal display device, the cell gap becomesabout 2 to 3 μm for a reflection type liquid crystal display device, andthe cell gap becomes 2 μm or less for a ferroelectric/antiferroelectricliquid crystal display device. Here, the photosensitive polyimide film51 with a thickness of 3.2 μm is formed.

As a method of controlling the film thickness, it is appropriate that amethod of polishing the surface of the pre-baked photosensitivepolyimide film 51 by a CMP treatment to a desired thickness is used.

Next, the photosensitive polyimide film 51 is patterned. As shown inFIG. 6C, the photosensitive polyimide film 51 is covered with aphotomask 52, and is irradiated with ultraviolet rays from the side ofthe mask 52. After a developing treatment, post baking at 280° C. forone hour is carried out. In this way, as shown in FIG. 6D and FIGS. 5Ato 5C, the patterned cell gap holding members 511 are formed.

It is appropriate that the diameter of the cylinder of the gap holdingmember 511 is set to 1.5 to 2.5 μm, and the height is set to 2.0 to 5.0μm. In this embodiment, the diameter of the cylinder is set to 3.0 μmand in order to make the cell gap 3.0 μm, the height thereof in theopposite region 502 opposite to the matrix circuit is set to 3.2 μm. Theheight of the gap holding member 511 in the opposite regions 503 and 504opposite to the driver circuits becomes high by the thickness of theopposite electrode 510, color filter, and the like.

As shown in FIG. 5A, a plurality of gap holding members 511 areregularly disposed. As to their arrangement density, it is appropriatethat the members are formed so that the density becomes about 40 to 160pieces/mm² which is almost equal to that of conventional sphericalspacers. In this embodiment, the density is set to 50 pieces/mm2. Thearrangement of the gap holding members 511 is not limited to that shownin FIGS. 5A to 5C, but a user may suitably determine. For example, thegap holding members may be disposed at random, or may be disposed atregions other than a region opposite to a driver circuit.

As a material of the gap holding member 511, it is possible to use aphotosensitive resin material or a resist material in addition tophotosensitive polyimide. It is also appropriate that a thermosettingresin such as acryl, polyamide, or polyimide-amide is used.

The shape of the gap holding member 511 is not limited to a cylinder,but a cylindroid, streamline pole, or polygonal pole such as trianglepole or quadrangular pole may be used, and as long as the gap betweenthe TFT substrate and the opposite substrate can be controlled, anyshape may be adopted.

For example, after the state of FIG. 6D is obtained, an oxygen plasmaprocess is carried out, so that the gap holding member 511 may be shapedinto a trapezoid pole. By making the trapezoid pole, it is possible toabsorb the impact received by the gap holding member 511 in a subsequentrubbing process of an orientation film.

Here, although the gap holding members 511 are formed on the oppositesubstrate side, they may be formed on the TFT substrate side by usingthe foregoing steps.

Next, as shown in FIG. 6E, an orientation film 512 is formed. A verticaloriented type polyimide film is used for the material of the orientationfilm 512, and the polyimide film is applied by a spin coating method.Thereafter, temporary baking at 80° C. for 5 minutes is performed, andheating (true baking) is performed by feeding a hot wind of 180° C. toharden polyimide, so that the orientation film 512 is formed.

In FIG. 6E, although the orientation film 512 does not cover the sideand surface of the gap holding member 511, in this embodiment, since thepolyimide coating film is formed by a spin coating method, there is alsoa case where this polyimide film covers the side and surface of the gapholding member 511 a little. However, the thickness of the polyimidefilm is as very thin as several tens to hundred nm while the height ofthe gap holding member 511 is several μm, and since there is also a casewhere a complete film is not formed at a vertical portion such as aside, so that merely the orientation film 512 formed on the surface ofthe substrate 501 is shown in FIG. 6E.

Next, the surface of the orientation film 512 is subjected to a rubbingprocess with a buff cloth (fiber such as rayon or nylon) having a pilelength of 2 to 3 mm. At this time, for the purpose of preventingbreakage of the gap holding member 511, rubbing conditions, such as thekind of buff cloth, pile implant density, and rotation number of aroller, are set.

Then, as described in the embodiments 1 to 3, the sealing member isformed on the TFT substrate and the opposite substrate, and the liquidcrystal is sealed in. FIG. 5C shows a sectional structure of a liquidcrystal display device using the sealing member of the embodiment 1.

Although the gap holding member 511 of this embodiment substitutes for aconventional spherical spacer, since it is a member fixed to thesubstrate, handling of the substrate at manufacturing steps of thesealing member also becomes easy in the embodiments 1 to 3. Moreover,the height of the holding member 511 can be set arbitrarily, so that thesize of the cell gap can be determined arbitrarily, which isparticularly useful for the case of a narrow cell gap of 2 μm or less ina ferroelectric liquid crystal display device or the like.

According to the foregoing embodiments 1 to 4, the display device ismade miniaturized and lightweight, so that the display device isparticularly suitable for a display device of a portable informationequipment, a note-sized or mobile computer, an electronic organizer, acar navigation system, or the like. Moreover, the display device is alsosuitable for a light bulb of a projector type display device in which anencasement of a final product is different from that of the displaydevice.

In the display device of the present invention, a sealing material isnot disposed on the surface of a substrate, but an adhesive layer isformed on the side of the substrate and a pair of substrates are bondedto each other, so that the size of the substrate can be reduced.Further, a tape or a frame member is provided closely to the outside ofthe adhesive layer, so that handling becomes easy and an outer frame formaking a module becomes unnecessary.

1. A display device comprising: a first substrate having an externalconnection terminal and a second substrate being bonded to each other,the first and second substrates being opposite to each other with a gapprovided therebetween; a pixel matrix circuit formed over the firstsubstrate; an adhesive layer being formed closely to the sides of thefirst and second substrates; and a frame member being formed closely tothe adhesive layer, wherein the frame member has a first window throughwhich the external connection terminal is connected to an FPC and asecond window over the pixel matrix circuit, and wherein the framemember has a liquid crystal injection port.
 2. The display deviceaccording to claim 1, wherein the frame member covers a periphery of anexposed surface of the first and second substrates.
 3. The displaydevice according to claim 1, wherein the frame member has heatconductivity higher than the adhesive layer.
 4. The display deviceaccording to claim 1, wherein the display device is an active matrixtype display device.
 5. The display device according to claim 1, whereinthe adhesive layer comprises a UV setting resin.
 6. The display deviceaccording to claim 1, wherein the adhesive layer comprises athermosetting resin.
 7. The display device according to claim 1, whereina sealing material is not formed on main surfaces of the first substrateand the second substrate.
 8. A display device comprising: a firstsubstrate having an external connection terminal and a second substratebeing bonded to each other, the first and second substrates beingopposite to each other with a gap provided therebetween; a pixel matrixcircuit and a driver circuit for driving the pixel matrix circuit, eachof the pixel matrix circuit and the driver circuit being formed over thefirst substrate; an adhesive layer being formed closely to the sides ofthe first and second substrates; and a frame member being formed closelyto the adhesive layer, wherein the frame member has a first windowthrough which the external connection terminal is connected to an FPCand a second window over the pixel matrix circuit, and wherein the framemember has a liquid crystal injection port.
 9. The display deviceaccording to claim 8, wherein the frame member covers a periphery of anexposed surface of the first and second substrates.
 10. The displaydevice according to claim 8, wherein the frame member has heatconductivity higher than the adhesive layer.
 11. The display deviceaccording to claim 8, wherein the display device is an active matrixtype display device.
 12. The display device according to claim 8,wherein the adhesive layer comprises a UV setting resin.
 13. The displaydevice according to claim 8, wherein the adhesive layer comprises athermosetting resin.
 14. The display device according to claim 8,wherein a seating material is not formed on main surfaces of the firstsubstrate and the second substrate.
 15. A display device comprising: afirst substrate having an external connection terminal and a secondsubstrate being bonded to each other, the first and second substratesbeing opposite to each other with a gap provided therebetween; a pixelmatrix circuit formed over the first substrate; an adhesive layer beingformed closely to the sides of the first and second substrates; and aframe member being formed closely to the adhesive layer, wherein theframe member has a first window through which the external connectionterminal is connected to an FPC and a second window over the pixelmatrix circuit, and wherein the frame member is in contact with thefirst substrate and the second substrate between the first window andthe second window.
 16. The display device according to claim 15, whereinthe frame member covers a periphery of an exposed surface of the firstand second substrates.
 17. The display device according to claim 15,wherein the frame member has heat conductivity higher than the adhesivelayer.
 18. The display device according to claim 15, wherein the displaydevice is an active matrix type display device.
 19. The display deviceaccording to claim 15, wherein the adhesive layer comprises a UV settingresin.
 20. The display device according to claim 15, wherein theadhesive layer comprises a thermosetting resin.
 21. The display deviceaccording to claim 15, wherein a sealing material is not formed on mainsurfaces of the first substrate and the second substrate.